Printing unit with short inking system in a rotary printing machine for direct printing using a &#34;waterless&#34; planographic printing plate

ABSTRACT

A printing unit of a rotary printing press utilizes a &#34;waterless&#34; planographic printing plate which is fastened on a printing cylinder. This &#34;waterless&#34; planographic printing plate receives ink from a short inking unit and directly prints a material to be printed. An additional printing cylinder, that is also equipped with a &#34;waterless&#34; planographic printing plate, acts as the counterpressure cylinder.

FIELD OF THE INVENTION

The invention relates to a printing unit of a rotary printing press witha short inking system for direct printing using a "waterless"planographic printing plate.

DESCRIPTION OF THE PRIOR ART

Printing units of rotary offset printing presses with short inkingsystems, wherein the ink to be printed on a paper web, is transferredindirectly by means of an offset cylinder--the rubber blanketcylinder--from a conventional, i.e. planographic printing plate providedwith dampening agent, to a paper web are generally known.

It is disadvantageous here that changes in the measurements of the papertake place because of the dampening agents transferred to the paper.

SUMMARY OF THE INVENTION

The invention is based on the object of providing a printing unit withan inking system for direct printing by means of a "waterless"planographic printing plate.

In accordance with the present invention, a printing unit of a rotaryprinting press utilizes a "waterless" planographic printing plate thatis secured on a printing cylinder. The printing unit is provided with ashort inking unit that includes a structured ink transfer roller and adoctor blade device. This short inking unit cooperates with the"waterless" planographic printing plate. A second printing cylinder,that is equipped with a second "waterless" planographic printing plateis provided and acts as the counterpressure cylinder for the printingunit.

The advantages which can be achieved by means of the present inventionreside, in particular, in that paper warping because of dampening agentsdoes not occur. Since no dampening agents are used, an assured inktransfer which remains constant is assured.

The printing cylinder with the soft "waterless" planographic printingplate takes over the function of the otherwise customary rubber blanketcylinder, and provides, for example, an even transfer of the pressureforce even with rough paper.

It is particularly advantageous that, because the rubber blanketcylinder is no longer needed, there is only one ink transfer pointbetween the planographic printing plate and the material to be printed,because of which less re-splitting and squeezing out of the printing inktakes place. Because of this, it is possible to transfer thickerprinting ink layers, which elsewhere are only achieved in connectionwith rotogravure or screen printing processes. Besides this, the presentprinting unit, without a rubber blanket cylinder, is considerablycheaper than comparable offset printing systems.

The use of a short inking system without ink zones for inking this"waterless" planographic printing plate is particularly advantageous,since, in this case, adjustment work for maintaining the ink transferconstant are omitted. In addition, the amount of waste is minimized. Thesimple construction makes maintenance work easier and the investmentcosts are extremely low.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention are represented in thedrawings and will be described in more detail below.

Shown are in:

FIG. 1, a schematic representation of a first preferred embodiment of aprinting unit in accordance with the present invention with a shortinking system;

FIG. 2, a schematic section through a planographic printing plate;

FIG. 3, a portion of a schematic section of a structured ink transferroller;

FIG. 4, a schematic representation of a second preferred embodiment of aprinting unit in accordance with the invention with a short inkingsystem; and

FIG. 5, a schematic representation of a third preferred embodiment of aprinting unit in accordance with the invention with a short inkingsystem.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A printing unit 2, in accordance with a first preferred embodiment ofthe present invention, and consisting of two printing cylinders 3, 4,wherein the second printing cylinder 4 acts as a counter-pressurecylinder for the first printing cylinder 3, is seated in lateral frames1 of a rotary printing press. This printing unit 2 is shown in FIG.1.

One "waterless" planographic printing plate 6 for direct printing isfastened on each of the printing cylinders 3, 4 shown in FIG, 1. Thisplanographic printing plate 6 has a metal or plastic support 7, a rubberlayer 8 applied to this metal support 7, a photosensitive resin layer 9applied to this rubber layer 8 and a silicon caoutchouc layer 11 appliedto this photosensitive resin layer 8 all as may be seen in FIG. 2. Theplanographic printing plate 6 is changed by means of known processes insuch a way, that the photosensitive resin layer 9 forms ink-accepting,printing areas 12, and the silicon caoutchouc layer 11 formsink-rejecting, non-printing areas 13. The soft rubber layer 8corresponds to an offset print rubber blanket. A material 14 to beprinted, for example a paper web, is directly printed between theprinting cylinders 3 and 4 from the respective "waterless" planographicprinting plate 6 supplied with ink, as seen in FIG. 1.

A short inking system 16, which is composed of a structured ink transferroller 17, and a doctor blade device 18, cooperates with this firstplanographic printing plate 6 carried on the first printing cylinder 3,and provides the planographic printing and plate 6 with printing ink 19.A printing ink 19 which is suitable for "waterless" planographicprinting, which is mixed with a parting agent 21, for example siliconoil or resins modified by silicon, is used as printing ink 19.

The ink transfer roller 17 consists of a steel core 22, which can havebearing journals. On its circumference, this steel core 22 is providedwith a coating 23 of a wear-resistant material, for example of a hardceramic material, which is applied by means of a spray method, forexample. This coating 23 is structured, in that depressions 24, forexample small cups or grooves, are engraved, for example by a laserprocess. Lands 26 which, for example, can intersect or extendapproximately parallel with each other, result between these depressions24. These lands 26 consist of wear-resistant, hard ceramic material andhave a high affinity to the part for which reason silicon oxide,aluminum oxide or chromium oxide, for example, which have been soaked insilicon oil or into which silicon rubber or fluorosilicon rubber hasbeen embedded, are used as the hard ceramic material.

The depressions 24 are lined with an ink-friendly coating 27, forexample a quinone diazid polymer substance all as depicted in FIG. 3.

The printing ink 19, mixed with parting agent 21, is supplied to thestructured ink transfer roller 17 by means of the doctor blade device18. This ink transfer roller 17 transfers the printing ink 19 directlyto the planographic printing plate 6, which inks printing areas 12 ofthe planographic printing plate 6 with printing ink 19, while theparting agent portion of the printing ink 19 is passed on tonon-printing areas 13 of the planographic printing plate 6.

It is, of course, possible to dispose any arbitrary number of inktransfer rollers between the first printing cylinder 3 and thestructured ink transfer roller 17. For example, with a short inkingsystem 28 and two further ink transfer rollers 29, 31 can be situatedbetween the first printing cylinder 3 and the structured ink transferroller 17 and can transfer printing ink 19. In this second preferredembodiment, ink transfer roller 29 resting against the structured inkfirst transfer roller 17 is provided with a soft coating, while thesecond ink transfer roller 31, which engages both the first planographicprinting plate 6 and the ink transfer roller 29 has a hard coating 33 asmay be seen by referring to FIG. 4.

In the third preferred embodiment of a short inking system 34 as shownin FIG. 5, two ink transfer rollers 36, 37 are disposed, and both touchthe "waterless" planographic printing plate 6 and also the structuredink transfer roller 17. The first ink transfer roller 36 has a soft,ink-friendly coating 38, and the second ink transfer roller 37 has asoft, parting agent-friendly coating 39, for example silicon rubber orfluorosilicon rubber.

While preferred embodiments of a printing unit with a short inking unitin a rotary printing machine for direct printing using a "waterless"planographic printing plate in accordance with the present inventionhave been set forth fully and completely hereinabove, it will beapparent to one of skill in the art that a number of changes in, forexample, the size of the printing press, the drive arrangement for theprinting cylinders, the type of web being printed and the like could bemade without departing from the true spirit and scope of the presentinvention which is accordingly to be limited to the following claims.

What is claimed is:
 1. A printing unit of a rotary printing presscomprising:a first printing cylinder; a first, soft waterlessplanographic printing plate secured to said first printing cylinder fordirectly printing a material to be printed, said first, soft waterlessplanographic printing plate having waterless ink accepting printingareas and waterless ink rejecting areas, said waterless ink rejectingareas being accepting of a waterless ink parting agent; a short inkingunit including at least one structured ink transfer roller and a doctorblade device, said short inking unit cooperating with said firstwaterless planographic printing plate, said structured ink transferroller having a plurality of depressions separated by a plurality oflands, said depressions being waterless ink accepting, said lands beingwaterless ink parting agent accepting, said doctor blade devicesupplying waterless printing ink to said structured ink transfer roller;a second printing cylinder; and a second, soft waterless planographicprinting plate secured to said second cylinder and forming acounterpressure cylinder for said first waterless planographic printingplate whereby a web is printed by passage between, and contact with saidfirst printing cylinder and said second printing cylinder.
 2. Theprinting unit of claim 1 wherein said short inking unit further includesfirst and second ink transfer rollers both of which contact saidstructured ink transfer roller and said first waterless planographicprinting plate.
 3. The printing unit of claim 2 wherein one of saidfirst and second ink transfer rollers is provided with a soft, partingagent-accepting coating.
 4. The printing unit of claim 2 wherein one ofsaid first and second ink transfer rollers is provided with a softink-accepting coating.
 5. The printing unit of claim 1 further includinga plurality of ink transfer rollers positioned between said structuredink transfer roller and said first waterless planographic printingplate.